The door on a FL should always be locked.
Even a slow tumble can twist your arm out of its socket.
The highest tumbling speeds used depend on drum size, but anything that lets clothes hit the drum higher than maybe 4 o'clock is no longer tumble cleaning clothes.
Distributions and spins in the wash are something used since the 80s over here.
Washing heavily relies on water going through clothing.
Be that by means of a recirculation spray, tumbling or high water levels doesn't really matter.
So, when lower water levels with larger loads in the same size drum became more common, distributions were implemented.
They basically provide a quick, efficient and easy way to exchange water between clothing and sump, especially with high volume loads.
My LG does distributions every 15min or so on larger loads.
On smaller loads it doesn't do them at all.
Also depends on cycle.